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11.
Roberta Colombo Raffaella Cerana Piera Lado Antonio Peres 《The Journal of membrane biology》1988,103(3):227-236
Summary The patch-clamp technique in whole-cell configuration was used to study the electrical properties of the tonoplast in isolated vacuoles fromAcer pseudoplatanus cultured cells. In symmetrical KCl or K2 malate solutions, voltage- and time-dependent inward currents were elicited by hyperpolarizing the tonoplast (inside negative), while in the positive range of potential the conductance was very small. The specific conductance of the tonoplast at –100 mV, in 100mm symmetrical KCl was about 160 S/cm2. The reversal potentials (E
rev) of the current, measured in symmetrical or asymmetrical ion concentrations (cation, anion or both) were very close to the values of the K+ equilibrium potential. Experiments performed in symmetrical or asymmetrical NaCl indicate that Na+ too can flow through the channels. NeitherE
rev nor amplitude and kinetics of the current changed by replacing NaCl with KCl in the external solution. These results indicate the presence of hyperpolarization-activated channels in tonoplasts, which are permeable to K+ as well as to Na+. Anions such as Cl– or malate seem to contribute little to the channel current. 相似文献
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The pigment of substantia nigra human brain has been extracted by a mild procedure consisting of washes with phosphate buffer, methanol and incubation with SDS-proteinase. Pyrolisis gas chromatography mass spectrometry infrared spectrometry, termogravimetric analysis and elemental analysis were the techniques used for the chemical characterization. An indole moiety bound to a sulfur containing amino acid and to palmitic acid were the main aspects found in the structure. The presence of a 7% inorganic component was observed. This probably contains Fe, Cu, Zn and Cr which are also relevant, for the formation and the role of melanin in substantia nigra neurons. The fatty acid moiety is chemically bound to the indole structure as it was not eliminated by repeated methanol washing. The same situation occurs for the sulfur containing gropu. Considering these data and the most abundant molecules present in substantia nigra the precursor of neuromelanin seems to be a cysteinyl-cethecol, to which is then bound a palmityl group. 相似文献
15.
Selection and characterization of transferrin receptor mutants using receptor-specific antibodies 总被引:1,自引:0,他引:1
Lymphoma cell lines were selected by growth in transferrin receptor-specific antibodies and in transferrin receptor-specific antibody coupled to ricin toxin. Sequential selections were used to isolate lines with multiple mutations affecting the transferrin receptor molecule. Mutant cell lines were characterized by their growth in antibody and their antibody-binding properties. Two basic types of mutations were found. One type resulted in the loss of a binding determinant for the antibody used for selection on one of the two transferrin receptor allelic products. The other type of mutation resulted in the loss of cell-surface expression of the entire gene product of one of the transferrin receptor alleles. 相似文献
16.
Relative Stability of Pertussis Vaccine Preserved with Merthiolate, Benzethonium Chloride, or the Parabens 总被引:2,自引:2,他引:0 下载免费PDF全文
When stored at 4 C, or heated at 22 or 35 C followed by storage at 4 C, the potency of pertussis vaccines preserved with Merthiolate was more stable than the potency of vaccines preserved with benzethonium chloride or the parabens (methyl- and propyl-p-hydroxybenzoate). Without preservative, potency was more stable than in the presence of benzethonium chloride or the parabens, but less stable than when Merthiolate was present. The histamine-sensitizing factor of the vaccines likewise decreased with the loss of potency. The deleterious effect of benzethonium chloride and the absence of the stabilizing effect of Merthiolate were contributing factors, if not the sole cause, for the instability of pertussis vaccine in quadruple antigen vaccine (diphtheria and tetanus toxoids and pertussis and poliomyelitis vaccines). 相似文献
17.
Mirella Ruggeri Michele Zoli Roberta Grimaldi Urban Ungerstedt Agneta Eliasson Luigi F. Agnati Kjell Fuxe 《Neurochemistry international》1990,16(4):427-435
Some methodological aspects of the intracerebral microdialysis technique have been investigated: the existence of a pressure gradient at the level of the dialyzing membrane, the substance diffusion from the microdialysis probe and the extent of tissue damage induced by the implantation of the microdialysis probe. At the level of the dialyzing membrane a rough balance between the pressure inside the probe and the one present in the extracellular fluid compartment has been observed. The pattern of substance diffusion in the tissue showed a large variability depending on the substance used and the experimental conditions. Relevant deductions can be made by the use of labeled markers. By means of this approach, the diffusion pattern of tritiated ganglioside GM1 in the tissue around the probe could be shown to follow a biexponential pattern, suggesting a two-step process of diffusion. The degree of tissue damage induced by the microdialysis probe was assessed by analyzing the glial reaction, and was measured by means of semiquantitative immunocytochemistry of glial fibrillary acidic protein immunoreactivity. Only a limited area of neuronal damage was observed in the region surrounding the microdialysis probe. The amount of glial reaction after probe implantation was shown to be comparable with that induced by the implantation of a microinjection cannula. 相似文献
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The arsenical resistance operon of IncN plasmid R46 总被引:3,自引:0,他引:3
Debby F. Bruhn Jiaxin Li Simon Silver Francisco Roberta Barry P. Rosen 《FEMS microbiology letters》1996,139(2-3):149-153
19.
Summary Endoproteinase(s) was isolated from a freeze-dried powder of larvae of Ostrinia nubilalis using reverse micellar solutions. The inhibition of proteinase was studied in reverse micelles with commercial Bowman-Birk soybean trypsin inhibitor and three trypsin inhibitors recently isolated from ripe cruciferous seeds. 相似文献
20.
Fine mapping of the Autosomal Dominant Split Hand/Split Foot Locus on Chromosome 7, Band q21.3-q22.1 总被引:6,自引:3,他引:3 下载免费PDF全文
Stephen W. Scherer Parvoneh Poorkaj Todd Allen Julia Kim Dorrit Geshuri Mark Nunes Sylvia Soder Karen Stephens Roberta A. Pagon Michael A. Patton Mary Anne Berg Tim Donlon Horacio Rivera R. A. Pfeiffer Kenji Naritomi Helen Hughes Maurizio Genuardi Fiorella Gurrieri Giovanni Neri Everett Lovrein Ellen Magenis Lap-Chee Tsui James P. Evans 《American journal of human genetics》1994,55(1):12-20
Split hand/split foot (SHFD) is a human developmental defect characterized by missing digits, fusion of remaining digits, and a deep median cleft in the hands and feet. Cytogenetic studies of deletions and translocations associated with this disorder have indicated that an autosomal dominant split hand/split foot locus (gene SHFD1) maps to 7q21-q22. To characterize the SHFD1 locus, somatic cell hybrid lines were constructed from cytogenetically abnormal individuals with SHFD. Molecular analysis resulted in the localization of 93 DNA markers to one of 10 intervals surrounding the SHFD1 locus. The translocation breakpoints in four SHFD patients were encompassed by the smallest region of overlap among the SHFD-associated deletions. The order of DNA markers in the SHFD1 critical region has been defined as PON–D7S812–SHFD1–D7S811–ASNS. One DNA marker, D7S811, detected altered restriction enzyme fragments in three patients with translocations when examined by pulsed-field gel electro-phoresis (PFGE). These data map SHFD1, a gene that is crucial for human limb differentiation, to a small interval in the q21.3-q22.1 region of human chromosome 7. 相似文献